The invention relates generally to video recording systems and, more particularly, to a method for determining the angular dimensions of a scene recorded by a video system.
During field tests of explosive devices and the like, remotely-disposed video systems often replace movie cameras used to record data during these field tests since the results, recorded on video tape, can be replayed on the spot for inspection. When dimensional information is to be extracted from the video data, the scene is displayed on the video monitor requires some form of calibration to eliminate the effects of system parameters. The angular dimensions of the field of view (or the dimensions of some part of it) are usually required in both the vertical and horizontal directions. When viewing a distant scene, the video system is sometimes calibrated by placing in the scene objects such as vertical poles, spaced a known distance apart at a known distance from the video camera. The angular separation and the angular height of the poles can be computed from the geometry of their deployment and the subsequent calibration of the scene on the video monitor can be accomplished.
The calibration of the video system by the use of poles and other known objects is subject to error. The calibration can only be as accurate as the measurement of the pole geometry. Often the optimal location for the poles may be in a hazardous or inaccessable area. At best, the deployment of the calibrating poles is a time consuming operation.